Dyslexia is a cognitive deficit in which a person's
reading and/or writing ability is significantly lower than that which would
be predicted by his or her general level of intelligence. People are diagnosed
as dyslexic when their reading problems cannot be explained by a lack of
intellectual ability, inadequate instruction, or sensory problems such as
poor eyesight. Because reading is a complex mental process, dyslexia has
many potential causes. From a neurophysiological perspective, dyslexia can
be diagnosed by close inspection of the morphology of the brain, usually
upon autopsy. Dyslexia is also associated with phonological difficulties,
such as enunciation.

Variations and related
disorders

Dyslexia is not a disease or a mental problem;
it is an orientation problem which can be compensated for (to some degree,
though never completely eradicated) with the proper tools. The dyslexic is
a three dimensional thinker. This gets in the way of being able to read because
written characters are two dimensional. The dyslexic tries to give a third
dimension which causes the problem. Dyslexics are usually above normal
intelligence because they have to be able to cope in a world where the other
80-85% of the population is oriented naturally. While there are theories
that an MRI done at school age can show differences in the dyslexic brain
patterns, these people can learn to cope in the world and be very successful.
Several famous people, such as Leonardo Da Vinci, Winston Churchill, Robin
Williams, Cher, Tom Cruise, Quentin Tarantino, and Ansel Adams have had this
condition. Scotopic sensitivity syndrome is a form of dyslexia which makes
it very difficult for a person to read black text on white paper, particularly
when the paper is slightly shiny.

In addition to the typical forms of dyslexia,
there are numerous related disorders:

* Dyscalculia- a neurological disorder characterised
by a problem with learning fundamentals and one or more of the basic numerical
skills. Often people with this disorder can understand very complex mathematical
concepts and principles but have difficulty processing formulas and even
basic addition and subtraction.

Facts and
statistics

5-15% of the population can be diagnosed as suffering
from various degrees of dyslexia.

Dyslexia and other similar disabilities are much
more commonly reported in males than in females. Most researchers agree that
there is a fairly even gender balance amongst dyslexics, but that the acted-out
frustration of dyslexic boys tends to draw more attention from teachers.
Since referrals for special education service are linked to such attention,
classes and programs designed to help such children often have more boys
than girls in them.

Studying dyslexia is very valuable for understanding
intelligence and creativity. Dyslexia illustrates the power of inborn wiring
of the brain in developing mental skills. At the same time it can show how
inborn limitations can be overcome by using the compensatory power of the
brain.

Dyslexia's main manifestation is a difficulty
in developing reading skills in elementary school children. Those difficulties
result from reduced ability to link up visual symbols with sounds. In the
past, dyslexia was mistakenly thought to have a motivational background.
Contrary to that erroneous belief, modern research has shown that dyslexia
is a condition largely inborn. In other words, dyslexia is a condition that
children are born with and not the result of poor parenting or the environment.
Some have disagreed with these findings, however, and believe that while
dyslexia may sometimes be inborn it is often attributable to lack of phonics
training when learning to read and the preponderance of the whole language
system.

Researchers studying the brains of dyslexics
have found that in reading tasks dyslexics show reduced activity in the left
inferior parietal cortex. Otherwise, dyslexics are known to often show higher
than average intelligence. There are marked anatomical differences between
dyslexic brains and normal brains.

Physiology and
treatment

Even a few weeks of intense phonological training
(often involving breaking down and rearranging sounds to produce different
words) can help noticeably improve reading skills. Unlike in normal adults,
phonological training shows an increase in the activity in the right
temporoparietal cortex.

This part of the brain works in spatial tasks
and may be the main compensatory structure in phonological training. This
is the sister region of the left temporoparietal cortex responsible for visual
motion processing which is underactive in many dyslexics. The earlier the
phonological regimen is taken on, the better the overall result. Advanced
brain scans could identify children at risk of dyslexia before they can even
read, although it is thought that simple tests of balance could do the same.
It has also been shown that early diagnosis and treatment can almost completely
redidiate the symptoms of dyslexia.

One hypothesis for some of the symptoms of dyslexia
is a lack of overall short-term memory. Typically a dyslexic will not remember
your name, and will suffer an undue amount of difficulty in transcribing
(for example) a phone number. These problems could be attributed to difficulty
in laying down short-term memories.

It is not that uncommon for dyslexics who have
trained themselves to cope with their affliction, to develop uncannily efficient
visual memories which aid in reading and comprehending large quantities of
information much faster than is typical. Adversely, some dyslexics may show
a natural dislike of reading and, in consequence, compensate by developing
unique verbal communication skills, inter-personal expertise, and leadership
skills. Different people adopt different strategies for living with the same
affliction.

A popular hypothesis for the reading difficulties
experienced by dyslexics is difficulty in bringing both eyes into focus on
the same point. Such problems explain why dyslexics often confuse the sequence
of written letters or numbers, as the end of the word is literally being
seen first by one eye, then the beginning of the word is seen by the other
eye. Studies in which young children are taught reading skills while wearing
an eyepatch have shown very promising results. This is based upon the theory
that, because children benefit more from learning to read than being confocal,
the former should take precedence over the latter.

In 1979, anatomical differences in the brain
of a young dyslexic were documented. Albert Galaburda of Harvard Medical
School noticed that language centers in dyslexic brains showed microscopic
flaws known as ectopias and microgyria. Both affect the normal six-layer
structure of the cortex. An ectopia is a collection of neurons that have
pushed up from lower cortical layers into the outermost one. A microgyrus
is an area of cortex that includes only four layers instead of six.

These flaws affect connectivity and functionality
of the cortex in critical areas related to sound and visual processing. These
and similar structural abnormalities may be the basis of the inevitable and
hard to overcome difficulty in reading.

Several genetic regions on chromosomes 1 and
6 have been found that might be linked to dyslexia. In all likelihood, dyslexia
is a conglomeration of disorders that all affect similar and associated areas
of the cortex. With time, science is likely to identify and classify all
individual suborders with benefits to our understanding of how low-level
genetic flaws can affect the wiring of the brain and enhance or reduce a
particular component of human mental capacity.

Some studies have concluded that speakers of
languages whose orthography has a strong correspondence between letter and
sound (e.g. Korean and Italian) have a much lower incidence of dyslexia than
speakers of languages where the letter is less closely linked to the sound
(e.g. English and French).

Whether today's models of dyslexia are correct
or not, the main lesson of dyslexia is that minor genetic changes affecting
the layering of the cortex in a minor area of the brain may impose inborn
limitations on the overall intellectual function. At the same time, dyslexia
shows that the brain exhibits a strong ability to compensate for its inborn
or acquired limitations, and intense training can often result in miraculous
turnabouts.

Lack of public
support

In the United States and in the United Kingdom,
some people say that there is a lack of adequate support and a general lack
of interest in the learning disabilities of children in public schools. This
has recently lead to legal action by private parties against public schools
in the United States and state schools in the United Kingdom.

In English law, the failure of schools to diagnose
and provide remedial help for dyslexia became grounds for personal injury
litigation in 1999 following a House of Lords decision in the case of Pamela
Phelps. Students with dyslexia in Higher Education may receive support funded
via the Disabled Students Allowance. Support can take the form of IT equipment
(software and hardware) as well as personal assistance, also known as non-medical
helper support. Dyslexic students will also be entitled to special provision
in examinations such as additional time to allow them to read and comprehend
exam questions.

The British Disability Discrimination Act also
covers dyslexia.

"In some cases, people have 'coping strategies'
which cease to work in certain circumstances (for example, where someone
who stutters or has dyslexia is placed under stress). If it is possible that
a person's ability to manage the effects of the impairment will break down
so that these effects will sometimes occur, this possibility must be taken
into account when assessing the effects of the impairment."

[Paragraph A8, Guidance to the Definitions of
Disability]

The information above is not intended
for and should not be used as a substitute for the diagnosis and/or treatment
by a licensed, qualified, health-care professional. This article is licensed
under the GNU Free Documentation
License. It incorporates material originating from the Wikipedia article
"Dyslexia".